Acute VIth cranial nerve dysfunction in multiple sclerosis. Evaluation by magnetic resonance imaging.

VIth nerve palsy is not frequently considered a presenting sign of multiple sclerosis (MS); however, MS has been documented as a fairly common cause of VIth nerve dysfunction. In the present study we have evaluated the clinical features and magnetic resonance imaging (MRI) findings in four MS patients with acute VIth nerve palsy. Diplopia as a result of acute VIth nerve palsy was the prominent symptom leading to the diagnosis of MS in all of the individuals. Other signs specifically localizing to the ipsilateral brainstem were absent in these patients. Cranial MRI revealed multiple white matter lesions with a periventricular predominance in all four patients and pontine white matter lesions in three of the patients. These lesions were either adjacent to the VIth nerve nucleus or involved the fasciculus of the VIth nerve or both.